A liquid crystal display device is now being widely used in a TV, a monitor for personal computers, and the like, because it is a display device with low electrical power consumption and it can be reduced in weight and thickness. The liquid crystal display device is not a self-emitting display device and it displays images using light from a backlight. An amount of the light from the back light is adjusted by electrically controlling alignment of liquid crystal molecules arranged between a pair of substrates (an active matrix substrate and a color filter substrate). Such a liquid crystal display device is commonly disadvantageous in viewing angle characteristics, and, so its characteristics need to be improved.
In order to improve the viewing angle characteristics of the liquid crystal display device, an alignment division technology in which one pixel is divided into two or more regions different in a tilt direction of liquid crystal molecules is now being researched and developed. According to this technology, the viewing angle characteristics can be improved by tilting the liquid crystal molecules in each pixel in different directions by voltage application to a liquid crystal layer. The respective regions which differ in the alignment (tilt) direction of the liquid crystal molecules are also called domain. The alignment division is also called multi-domain.
As the multi-domain liquid crystal display devices, examples of horizontal alignment liquid crystal display devices include: a multi-domain TN (twist nematic) liquid crystal display device; a multi-domain ECB (electrically controlled birefringence) liquid crystal display device; and a multi-domain OCB (optically compensated birefringence) liquid crystal display device. In addition, examples of vertical alignment liquid crystal display devices include: a MVA (multi-domain vertical alignment) liquid crystal display device; a PVA (patterned vertical alignment) liquid crystal display device; a multi-domain VAECB (vertical alignment electrically controlled birefringence) liquid crystal display device; a multi-domain VAHAN (vertical alignment hybrid-aligned nematic) liquid crystal display device; and a multi-domain VATN (vertical alignment twisted nematic) liquid crystal display device. These various liquid crystal display devices are now being further developed in order to show improved viewing angle characteristics.
A rubbing method, a photo-alignment method, and the like, are mentioned as a method for the alignment division. In the rubbing method, for example, an alignment film is rubbed, with a rubbing region and a non-rubbing region being separated from each other by a resist pattern. According to such a rubbing method, the alignment film surface is provided with the alignment treatment by being rubbed with a cloth wound on a roller. In this method, dust such as a fiber of the cloth and rubbed scrapes are generated, and further, static electricity generated due to the fiber of the cloth might cause defects such as malfunction, a change in characteristics, and deterioration, of switching elements.
In the photo-alignment method, a photo-alignment film is used as a material for the alignment film, and the photo-alignment film is exposed to light such as ultraviolet light, and thereby the alignment film is provided with an alignment regulating force and/or an alignment regulating direction of the alignment film is changed. Thus, in the photo-alignment method, the alignment film can be subjected to the alignment treatment in a contact-less manner. Therefore, soils, dusts, and the like, which are generated by the alignment treatment, can be reduced. In addition, in the photo-alignment method, by exposing the alignment film through a pattern photomask including transmissive parts formed in a desired pattern, desired regions in the alignment film plane can be photo-irradiated under various conditions. As a result, domains having a desirable design can be easily formed.
The following technologies are disclosed as the photo-alignment method. Patent Document 1 discloses that an opening is formed along a boundary between domains, for example. Further, for example, Patent Document 2 discloses that at a boundary between domains, a region where liquid crystal molecules are aligned differently from those in the domains is arranged.
According to a common liquid crystal display device, a light-shielding layer for shielding light from a backlight is arranged in a frame region (non-display region), which is positioned surrounding a display region where images (moving images) are displayed. A resin black matrix (BM), which is formed in a color filter substrate, is generally used as the light-shielding layer.
Lately, in order for the liquid crystal display device to show a higher response speed, a distance between substrates (cell thickness) is decreased. So the BM is also formed to have a very small thickness. As a result, a transmittance of light that passes through the BM is increased, which causes light leakage from the frame region. This light leakage might have adverse effects on images displayed in the display region. Accordingly, in the conventional liquid crystal display device, display qualities in the display region close to the frame region need to be further improved.
In order to improve display qualities in the display region close to the frame region, the following technology is disclosed. For example, Patent Document 3 discloses that light leakage from an edge of a display region is suppressed by arranging a light shield device between drawing wirings (outgoing lines) formed in a frame region. If the light shield device is arranged to cover adjacent two drawing wirings and if one of the adjacent two drawing wings and the light shield device are leaked because of a film formation defect of an interlayer insulating film that is formed between the drawing wirings and the light shield device, the light shield device covers the other drawing wiring into which a different signal is fed. As a result, the adjacent two drawing wirings are influenced by each other's signals. If a film formation defect between one of adjacent two drawing wirings and the light shield device and a film formation defect between the other drawing wiring and the light shield device are generated, the two drawing wirings are leaked through the light shield. So the drawing wirings and the light shield device need to be arranged with a distance therebetween. However, if the distance between the drawing wiring and the light shield device is large, the light shield device can not sufficiently shield light from the backlight, and so light leakage deteriorates display qualities. If the distance between the drawing wiring and the light shield device is small and if a residual metal film after the drawing wiring is formed is electrically connected to adjacent two drawing wirings, this electrical connection might not be corrected because the correction might cause some defects, for example, in the following case: if this residual metal film is removed by laser to cut the electrical correction, the light shield device might be also welded.    [Patent Document 1]
Japanese Kokai Publication No. 2000-257646    [Patent Document 2]
Japanese Kokai Publication No. 2002-31804    [Patent Document 3]
U.S. Pat. No. 6,975,377